The Experts below are selected from a list of 8892 Experts worldwide ranked by ideXlab platform
V Dose - One of the best experts on this subject based on the ideXlab platform.
-
decomposition of multicomponent mass spectra using bayesian probability theory
Journal of Mass Spectrometry, 2002Co-Authors: H D Kang, R Preuss, T Schwarzselinger, V DoseAbstract:We present a method for the decomposition of the mass spectra of mixed Gases using Bayesian probability theory. The method works without any calibration measurement and therefore applies also to the analysis of spectra containing unstable species. For the example of mixtures of three different Hydrocarbon Gases the algorithm provides concentrations and cracking coefficients of each mixture component and also their confidence intervals. The amount of information needed to obtain reliable results and its relation to the accuracy of our analysis are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
-
decomposition of multicomponent mass spectra using bayesian probability theory
arXiv: Data Analysis Statistics and Probability, 2002Co-Authors: H D Kang, R Preuss, T Schwarzselinger, V DoseAbstract:We present a method for the decomposition of mass spectra of mixture Gases using Bayesian probability theory. The method works without any calibration measurement and therefore applies also to the analysis of spectra containing unstable species. For the example of mixtures of three different Hydrocarbon Gases the algorithm provides concentrations and cracking coefficients of each mixture component as well as their confidence intervals. The amount of information needed to obtain reliable results and its relation to the accuracy of our analysis are discussed.
Alexei V Milkov - One of the best experts on this subject based on the ideXlab platform.
-
molecular and stable isotope compositions of natural gas hydrates a revised global dataset and basic interpretations in the context of geological settings
Organic Geochemistry, 2005Co-Authors: Alexei V MilkovAbstract:Abstract A global dataset of molecular and stable isotope compositions of Gases released from 209 different specimens of natural gas hydrate is presented and discussed. The 26 hydrate-bearing areas from 21 geographic regions are grouped into high gas flux (HGF) settings, low gas flux (LGF) settings and hydrated gas accumulations (HGA). Methane (CH4) is the most abundant hydrate-bound gas, while CO2 and C2+ Hydrocarbon Gases are frequently present in small amounts. Non-Hydrocarbon Gases, such as H2S, are uncommon. The stable isotope composition of hydrate-bound Gases varies significantly (e.g., δ13C of CH4 from −74.7 to −39.6‰), suggesting that Gases of both microbial and thermogenic origin form gas hydrates. Hydrate-bound Gases are derived from autochthonous [located predominantly within the gas hydrate stability zone (GHSZ)] and allochthonous (located in deep sediments) sources. The occurrence and concentration of gas hydrates in sediments are controlled not by the origin of Gases, but rather by their sources, which in turn strongly depend on geological setting. Allochthonous Gases (microbial and/or thermogenic) dominate in HGF and HGA settings where they are focused in the shallow GHSZ along faults, within mud volcanoes, in permeable carrier beds and other geological features from underlying petroleum systems. Relatively high concentrations of gas hydrate (average 5–15% of pores and locally up to 100% of volume) occurring over small areas are typical of HGF and HGA settings. In contrast, autochthonous and diffuse allochthonous Gases (mostly microbial) occur in stratigraphically and structurally simple LGF settings and result in relatively low concentrations of gas hydrate (average ∼2% of pores in the GHSZ) spread over large areas. The major implication of this finding is that successful prediction of resource and geohazard potential of gas hydrates is possible only if regional petroleum systems extending well below the GHSZ are properly evaluated. In addition to the diagnosis of origins and sources of hydrate-bound Gases, molecular and isotopic data help to better identify hydrate-bearing intervals and provide valuable insights into the dynamics of hydrate-bearing sites.
-
thermogenic gas hydrates and Hydrocarbon Gases in complex chemosynthetic communities gulf of mexico continental slope
Organic Geochemistry, 1999Co-Authors: Roger Sassen, Samantha B Joye, Stephen T Sweet, Debra A Defreitas, Alexei V Milkov, Ian R MacdonaldAbstract:Abstract Where abundant at the sea floor, thermogenic gas hydrates impact bacterially-mediated processes in chemosynthetic communities dependent on methane and H2S. Our main gas hydrate sites are at ∼540 m water depth and relatively low temperature (∼7°C). Gas hydrates outcrop as vein-fillings in hemipelagic muds near gas vents within chemosynthetic communities. Molecular and isotopic properties of hydrate-forming C1–C5 Hydrocarbons and CO2 provide insight to bacterially-mediated processes. Hydrate-bound methane is altered by bacterial oxidation, as indicated by enrichment of 13C and deuterium (D), and by CO2 depleted in 13C. The degree of gas hydrate alteration appears related to duration of exposure at the sea floor. In hydrate-associated sediments, bacterial oxidation of a mixed pool of Hydrocarbons yields a net production of CO2 depleted in 13C. Bacterial oxidation of hydrate-bound methane and free Hydrocarbon Gases in adjacent sediments could contribute to gas hydrate decomposition. Some thermogenic carbon in sediments could be recycled via methanogenesis to yield a net production of bacterial methane depleted in 13C. Our results strengthen the hypothesis that gas hydrates could favor life in other extreme environments at low temperatures.
Laifei Cheng - One of the best experts on this subject based on the ideXlab platform.
-
fabrication and electromagnetic interference shielding effectiveness of carbon nanotube reinforced carbon fiber pyrolytic carbon composites
Carbon, 2014Co-Authors: Luo Kong, Quan Li, Wenyan Duan, Litong Zhang, Laifei ChengAbstract:Abstract Carbon nanotube reinforced carbon fiber/pyrolytic carbon composites were fabricated by precursor infiltration and pyrolysis method and their electromagnetic interference shielding effectiveness (EMI SE) was investigated over the frequency range of 8.2–12.4 GHz (X-band). Carbon nanotubes (CNTs) were in situ formed through catalyzing Hydrocarbon Gases evaporating out of phenolic resin with nano-scaled Ni particles. The content of CNTs increased with the increase of Ni loadings (0.00, 0.50, 0.75 and 1.25 wt.%) in phenolic resin. Thermal gravimetrical analysis results showed that the carbon yield of phenolic resin increased with the addition of Ni catalyst. With the formation of CNTs, the EMI SE increased from 28.3 to 75.2 dB in X-band. The composite containing 5.0 wt.% CNTs showed an SE higher than 70 dB in the whole X-band.
-
fabrication and electromagnetic interference shielding effectiveness of carbon nanotube reinforced carbon fiber pyrolytic carbon composites
Carbon, 2014Co-Authors: Xingmin Liu, Luo Kong, Wenyan Duan, Litong Zhang, Xiaowei Yin, Ye Liu, Laifei ChengAbstract:Abstract Carbon nanotube reinforced carbon fiber/pyrolytic carbon composites were fabricated by precursor infiltration and pyrolysis method and their electromagnetic interference shielding effectiveness (EMI SE) was investigated over the frequency range of 8.2–12.4 GHz (X-band). Carbon nanotubes (CNTs) were in situ formed through catalyzing Hydrocarbon Gases evaporating out of phenolic resin with nano-scaled Ni particles. The content of CNTs increased with the increase of Ni loadings (0.00, 0.50, 0.75 and 1.25 wt.%) in phenolic resin. Thermal gravimetrical analysis results showed that the carbon yield of phenolic resin increased with the addition of Ni catalyst. With the formation of CNTs, the EMI SE increased from 28.3 to 75.2 dB in X-band. The composite containing 5.0 wt.% CNTs showed an SE higher than 70 dB in the whole X-band.
H D Kang - One of the best experts on this subject based on the ideXlab platform.
-
decomposition of multicomponent mass spectra using bayesian probability theory
Journal of Mass Spectrometry, 2002Co-Authors: H D Kang, R Preuss, T Schwarzselinger, V DoseAbstract:We present a method for the decomposition of the mass spectra of mixed Gases using Bayesian probability theory. The method works without any calibration measurement and therefore applies also to the analysis of spectra containing unstable species. For the example of mixtures of three different Hydrocarbon Gases the algorithm provides concentrations and cracking coefficients of each mixture component and also their confidence intervals. The amount of information needed to obtain reliable results and its relation to the accuracy of our analysis are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
-
decomposition of multicomponent mass spectra using bayesian probability theory
arXiv: Data Analysis Statistics and Probability, 2002Co-Authors: H D Kang, R Preuss, T Schwarzselinger, V DoseAbstract:We present a method for the decomposition of mass spectra of mixture Gases using Bayesian probability theory. The method works without any calibration measurement and therefore applies also to the analysis of spectra containing unstable species. For the example of mixtures of three different Hydrocarbon Gases the algorithm provides concentrations and cracking coefficients of each mixture component as well as their confidence intervals. The amount of information needed to obtain reliable results and its relation to the accuracy of our analysis are discussed.
G F Slater - One of the best experts on this subject based on the ideXlab platform.
-
isotopic signatures of ch4 and higher Hydrocarbon Gases from precambrian shield sites a model for abiogenic polymerization of Hydrocarbons
Geochimica et Cosmochimica Acta, 2008Co-Authors: Sherwood B Lollar, K Voglesonger, Tullis C Onstott, Lisa M Pratt, Georges Lacrampecouloume, G F SlaterAbstract:Abstract Previous studies of methane and higher Hydrocarbon Gases in Precambrian Shield rocks in Canada and the Witwatersrand Basin of South Africa identified two major gas types. Paleometeoric waters were dominated by Hydrocarbon Gases with compositional and isotopic characteristics consistent with production by methanogens utilizing the CO 2 reduction pathway. In contrast the deepest, most saline fracture waters contained Gases that did not resemble the products of microbial methanogenesis and were dominated by both high concentrations of H 2 gas, and CH 4 and higher Hydrocarbon Gases with isotopic signatures attributed to abiogenic processes of water–rock reaction in these high rock/water ratio, hydrogeologically-isolated fracture waters. Based on new data obtained for the higher Hydrocarbon Gases in particular, a model is proposed to account for carbon isotope variation between CH 4 and the higher Hydrocarbon Gases (specifically ethane, propane, butane, and pentane) consistent with abiogenic polymerization. Values of δ 13 C for CH 4 and the higher Hydrocarbon Gases predicted by the model are shown to match proposed abiogenic Hydrocarbon gas end-members identified at five field sites (two in Canada and three in South Africa) suggesting that the carbon isotope patterns between the Hydrocarbon homologs reflect the reaction mechanism. In addition, the δ 2 H isotope data for these Gases are shown to be out of isotopic equilibrium, suggesting the consistent apparent fractionation observed between the Hydrocarbon homologs may also reflect reaction mechanisms involved in the formation of the Gases. Recent experimental and field studies of proposed abiogenic Hydrocarbons such as those found at mid-ocean spreading centers and off-axis hydrothermal fields such as Lost City have begun to focus not only on the origin of CH 4 , but on the compositional and isotopic information contained in the higher Hydrocarbon Gases. The model explored in this paper suggests that while the extent of fractionation in the first step in the Hydrocarbon synthesis reaction chain may vary as a function of different reaction parameters, δ 13 C values for the higher Hydrocarbon Gases may be predicted by a simple mass balance model from the δ 13 C values of the lower molecular weight precursors, consistent with abiogenic polymerization. Integration of isotopic data for the higher Hydrocarbon Gases in addition to CH 4 may be critical for delineation of the origin of the Hydrocarbons and investigation of formation mechanisms.